In XLL+ 6.2, we have significantly improved the implementation of asynchronous functions.

1. Asynchronous functions no longer need to have a special "RtdSignal" cell.
2. They now have exactly the same signature as standard synchronous functions.
3. There is a lower performance cost to running a function asynchronously.
4. The user experience is affected less - no cell formulae are changed, and the update is much less intrusive.

See Asychronous functions in the User Guide for more details.